1. Field of the Invention
The present invention relates to a throttle control device and a method for an internal combustion engine for controlling a throttle valve opening angle by driving a motor in accordance with accelerator depression.
2. Description of Related Art
A conventional throttle control for an internal combustion engine (electronic throttle system) throttle valve opening by driving a motor in accordance with accelerator depression amount or the like. For example, current is supplied to the motor in accordance with from an accelerator sensor signal detecting accelerator depression whereby the motor is driven to open or close the throttle valve and the amount of air supplied to an internal combustion engine is controlled. In this case, feedback control by proportional, integral and differential (PID) control is carried out to eliminate deviation between a throttle sensor signal detecting throttle opening angle and the accelerator sensor signal.
This device is disclosed in Examined Japanese Patent Publication No. 7-33781. In this device, a fuel amount based on accelerator depression or the like, is calculated and corresponding air amount for attaining a predetermined A/F (air-fuel ratio) is provided by controlling the throttle valve.
In this case, the fuel amount calculated from accelerator depression is estimated and calculated such that future operational condition is based on extension of the current operational condition. Meanwhile, when the accelerator is operated abruptly or in an otherwise complicated way, a discrepancy between the calculated fuel amount the requested fuel amount and A/F is varies significantly from the stoichiometric air-fuel ratio thereby deteriorating engine exhaust emission.